CAD Exchanger is now on Android

by - 10:16

CAD Exchanger is now available in Google Play. Free, with in-app purchase (larger file size support, export to B-Rep formats, and more features in the future). OCC 6.9.0+ and Qt (QML) 5.5.0 based.

I would like to thank again the OCC development team (Andrey B, Kirill G, Sergey A, Ivan and others) and management (Alexander T and Michael K) for their support in porting the OCC platform as a prerequisite. See more details in the official press-release.

We met for the first time in August 2014 and the folks did their major part in a couple of months or so. Sometimes it was a bumpy road with some hot discussions but all is well that ends well. On our side we were doing a parallel port of a major version 3.0 to a totally new data model and UI, as a prerequisite to Android port. With parallel jumps between Windows, Linux and Android, with their different IDE's and toolchains - all pleasures of cross-platform development. That took us way too much time and we missed the schedule a few times. I regret we did this 6+ months later than originally planned but still would like to thank my team - Sergey, Denis and others for their extra efforts. There were multiple fruitful forum topics, bug reports and fixes - some are herehere or in Mantis, so good working relationship between the teams has been strengthened.

Among technical highlights there are probably a few interesting items - for instance an asynchronous, non-blocking visualization workflow (see discussion preview here). When we have some free cycles, we will try to share more technical details.

Meanwhile, if you have some spare time, please give a try to a brand new CAD Exchanger version and share your thoughts via Google Play, here or just email us at We'd *really* be happy to hear from the community. Constructive critic, recommendations or positive comments are all valuable.

And please do keep CAD Exchanger on your device, you now know some people behind it ;-).

Thanks for your time and take care,

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  1. Congrats Roman, a huge achievement, got it on my nexus phone ;)

  2. Btw, the non-blocking viz. workflow is a big deal... thanks for pushing that one!

  3. So I see cad exchanger is only able to be installed on tablets, not phones?

  4. Hi Jelle,
    Thank you for your support. CAD Exchanger should run on phones (we did have engineering versions running). The point is that the layout has not been optimized for phones yet, so user experience can be suboptimal.
    We certainly have phone port on our roadmap.
    Thanks again,

  5. hi Roman,

    Ah, so i tried installing through google play, but its stated that the app isnt compatible with my phone, which is an LG nexus 5

  6. Too bad. Sorry Jelle. I've filed a bug report to our developers for them to check. Please stay tuned.

  7. Hi Roman,

    I've just started to work on porting some of the pythonocc code to QML.
    I read that a lot of hard work was done such to port OCC to be able to utilize QML, right? I'm working on refactoring the GL widget to use Qt5's QOpenGLWidget rather than Qt4's QGLWidget. Can you comment on the minimal OCC version to be able to use QOpenGLWidget? Is that 6.8.0? IIRC that's the first demonstrating CAD Assistant / running on android, right?

    Thanks! I think you guys have been sponsoring this transition, and I'm really looking fwd combining (python)OCC and QML...


  8. Hi Jelle,

    The minimal appropriate OCC version is 6.9.0. You might certainly want to refer to samples/qt/AndroidQt.

    A couple of notes on peculiarities which we had to take into account:
    - connection to existing OpenGL context;
    - use of shaders instead of fixed pipeline
    - dedicated threads to UI, rendering and computations;
    - use of FBO.

    Good luck with the port!

  9. Hello Roman,

    Could you maybe elaborate how you did setup OCC to render into an FBO and render that FBO into a QQuickItem?

    I tried with something based on

    But I cannot get it to work. Maybe the QQuickFrameBufferObject is not the way to go because it itself is already an FBO

    Would really appreciate it,


  10. Hi Dirk,

    Sorry for getting that long to respond - although on my TODO list your inquiry got buried too quickly with other stuff.
    Anyway, if that is still relevant here are some tips shared by our lead GUI developer who made that QML/Android port:
    There are two approached to combine OCC rendering with Qt 5:

    1. Render OCC to Qt Quick Window directly when "beforeRendering" signal is emitted.

    See AndroidQt occ 7.0.0 sample and "OpenGL Under QML" Qt example (

    Pros of this approach are:
    - minimum actions to use OCC with QtQuick;

    direct rendering to window (so it take all window space), so you cannot use QtQuickItem transformations, rotations, effects, etc.

    2. Render OCC to QtQuickFrameBuffer.
    OCC cannot use QtQuickFrameBuffer for rendering, but you can use as follows: render to OCC frameBuffer (see V3d_View::ToPixMap method as reference), then blit OCC frame buffer to Qt frame buffer (see OpenGl_View::blitBuffers method as reference).

    - full compatibility with recommended Qt Quick item rendering;
    - all features in Qml code;

    - complicated implementation and some memory overhead;
    - OCC frameBuffer size should be kept in sync with Qt frameBuffer size;
    - Qt Quick use multi-threading rendering, so you should guarantee all OCC rendering methods be called in a dedicated render thread.

    Hope this will give you some food for thought.
    Good luck!

  11. Thanks for the hints Roman!

    I will take a look!


  12. Hi Roman,

    I finally had some time again to play with qml and OCC and managed to implement rendering by using a framebuffer and bltting the OCC FBO in the QQuickFramebufferObject::Renderer derived class.

    Now I am trying to implement mouse interaction and my first attempt was to queue all the important mouse messages and synchronize them in the renderer. Then in the render function I loop through all the messages in the queue and call view->Rotation view->Pan which now render in the FBO accordingly. If the queue is not empty I call update which schedules to call render again. This works but mouse interaction and visually seeing the result lags behind a bit. It feels more natural if the changes are immediate. How did you solve mouse interaction if I may ask?

    Kind regards,


    1. Hi Dirk,

      Do you have a sample for the above mentioned success ?

  13. Hi Dirk,

    We collapse sequential events of the same kind in the queue and only process the resulting one.

    Qt mouse events can be emitted very often (once every 1-2 ms), but rendering occurs less often. If to process all the events in order, the renderer will spend a lot of time for rendering: every view manipulation will require a piece of time. But during frame rendering a lot of new mouse event will be received and they will be processed only on the next frame rendering. So we use mouse event reducing before view manipulation to avoid unnecessary time spending.

    For instance, the renderer received:
    1. Pan mouse event
    2. Pan mouse event
    3. Pan mouse event
    4. Rotation mouse event
    5. Rotation mouse event
    6. Rotation mouse event

    What you can do with events:
    1. Start panning.
    2. Merge with previous event.
    3. Merge with previous event.
    4. Finish panning (because a new operation has been detected). Start rotation.
    5. Merge with previous event.
    6. Merge with previous event.
    7. Finish rotation (because no events in the queue).

    As a result only important updates can be applied to the 3D view.

    Just in case, we provide a simple visualization example based on Qt/QML. Of course, it's connected to CAD Exchanger SDK but if this is something you are open to consider, just let me know.

    Good luck!

  14. Hi Roman,

    Thanks very much, makes perfect sense!


  15. Hi Roman,

    This makes perfect sense! Thanks very much.
    I replied earlier but it didn't come through so it seems.


  16. Sure Dirk! Glad this helped. Good luck!